diff --git a/.eslintignore b/.eslintignore
index b11848f7acbd..58f1acb45c7c 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -156,6 +156,11 @@ dom/workers/test/importScripts_worker_imported3.js
 dom/workers/test/invalid.js
 dom/workers/test/threadErrors_worker1.js
 
+# Tests the module loader's path handling.
+# Dynamic imports contains non-optimal paths.
+dom/workers/test/xpcshell/data/base_uri_worker.js
+dom/workers/test/xpcshell/data/base_uri_module.mjs
+
 # Bug 1527075: This directory is linted in github repository
 intl/l10n/
 
diff --git a/dom/quota/test/modules/system/worker/Utils.js b/dom/quota/test/modules/system/worker/Utils.js
index ca9b54a92aa3..b8e6224bf4fd 100644
--- a/dom/quota/test/modules/system/worker/Utils.js
+++ b/dom/quota/test/modules/system/worker/Utils.js
@@ -10,25 +10,11 @@ async function ensureUtilsChild() {
     return;
   }
 
-  try {
-    const { UtilsChild: importedUtilsChild } = await import(
-      "/dom/quota/test/modules/worker/UtilsChild.js"
-    );
+  const { UtilsChild: importedUtilsChild } = await import(
+    "/dom/quota/test/modules/worker/UtilsChild.mjs"
+  );
 
-    UtilsChild = importedUtilsChild;
-
-    throw Error("Please switch to dynamic module import");
-  } catch (e) {
-    if (e.message == "Please switch to dynamic module import") {
-      throw e;
-    }
-
-    importScripts("/dom/quota/test/modules/worker/UtilsChild.js");
-
-    const { UtilsChild: importedUtilsChild } = globalThis.importUtilsChild();
-
-    UtilsChild = importedUtilsChild;
-  }
+  UtilsChild = importedUtilsChild;
 }
 
 const Utils = {
diff --git a/dom/quota/test/modules/system/worker/UtilsChild.js b/dom/quota/test/modules/system/worker/UtilsChild.mjs
similarity index 91%
rename from dom/quota/test/modules/system/worker/UtilsChild.js
rename to dom/quota/test/modules/system/worker/UtilsChild.mjs
index 4addd6b94809..d3b5455a59df 100644
--- a/dom/quota/test/modules/system/worker/UtilsChild.js
+++ b/dom/quota/test/modules/system/worker/UtilsChild.mjs
@@ -24,7 +24,7 @@ function _recvMessage() {
   });
 }
 
-const _UtilsChild = {
+export const UtilsChild = {
   async getCachedOriginUsage() {
     _sendMessage({
       op: "getCachedOriginUsage",
@@ -50,7 +50,3 @@ const _UtilsChild = {
     return _recvMessage();
   },
 };
-
-function importUtilsChild() {
-  return { UtilsChild: _UtilsChild };
-}
diff --git a/dom/quota/test/moz.build b/dom/quota/test/moz.build
index c01a46c55205..4f7fdc88c8cc 100644
--- a/dom/quota/test/moz.build
+++ b/dom/quota/test/moz.build
@@ -82,5 +82,5 @@ TESTING_JS_MODULES.dom.quota.test.modules.worker += [
     "modules/system/worker/head.js",
     "modules/system/worker/ModuleLoader.js",
     "modules/system/worker/Utils.js",
-    "modules/system/worker/UtilsChild.js",
+    "modules/system/worker/UtilsChild.mjs",
 ]
diff --git a/dom/script/ScriptLoader.cpp b/dom/script/ScriptLoader.cpp
index 4f1b1558601d..c847b133fde0 100644
--- a/dom/script/ScriptLoader.cpp
+++ b/dom/script/ScriptLoader.cpp
@@ -3675,11 +3675,6 @@ int32_t ScriptLoader::PhysicalSizeOfMemoryInGB() {
   return mPhysicalSizeOfMemory;
 }
 
-static bool IsInternalURIScheme(nsIURI* uri) {
-  return uri->SchemeIs("moz-extension") || uri->SchemeIs("resource") ||
-         uri->SchemeIs("chrome");
-}
-
 bool ScriptLoader::ShouldApplyDelazifyStrategy(ScriptLoadRequest* aRequest) {
   // Full parse everything if negative.
   if (StaticPrefs::dom_script_loader_delazification_max_size() < 0) {
@@ -3866,13 +3861,7 @@ nsresult ScriptLoader::PrepareLoadedRequest(ScriptLoadRequest* aRequest,
   rv = channel->GetOriginalURI(getter_AddRefs(uri));
   NS_ENSURE_SUCCESS(rv, rv);
 
-  // Fixup moz-extension: and resource: URIs, because the channel URI will
-  // point to file:, which won't be allowed to load.
-  if (uri && IsInternalURIScheme(uri)) {
-    aRequest->mBaseURL = uri;
-  } else {
-    channel->GetURI(getter_AddRefs(aRequest->mBaseURL));
-  }
+  aRequest->SetBaseURLFromChannelAndOriginalURI(channel, uri);
 
   if (aRequest->IsModuleRequest()) {
     ModuleLoadRequest* request = aRequest->AsModuleRequest();
diff --git a/dom/workers/loader/NetworkLoadHandler.cpp b/dom/workers/loader/NetworkLoadHandler.cpp
index 4157e6e3b9a3..9c2c24306650 100644
--- a/dom/workers/loader/NetworkLoadHandler.cpp
+++ b/dom/workers/loader/NetworkLoadHandler.cpp
@@ -188,7 +188,7 @@ nsresult NetworkLoadHandler::DataReceivedFromNetwork(nsIStreamLoader* aLoader,
   rv = channel->GetOriginalURI(getter_AddRefs(uri));
   NS_ENSURE_SUCCESS(rv, rv);
 
-  channel->GetURI(getter_AddRefs(loadContext->mRequest->mBaseURL));
+  loadContext->mRequest->SetBaseURLFromChannelAndOriginalURI(channel, uri);
 
   // Figure out what we actually loaded.
   nsCOMPtr<nsIURI> finalURI;
diff --git a/dom/workers/test/xpcshell/data/base_uri_module.mjs b/dom/workers/test/xpcshell/data/base_uri_module.mjs
new file mode 100644
index 000000000000..7604baed8227
--- /dev/null
+++ b/dom/workers/test/xpcshell/data/base_uri_module.mjs
@@ -0,0 +1,23 @@
+// This file is for testing the module loader's path handling.
+// ESLint rules that modifies path shouldn't be applied.
+
+export const obj = {};
+
+export async function doImport() {
+  // This file is loaded as resource://test/data/base_uri_module.mjs
+  // Relative/absolute paths should be resolved based on the URI, instead of
+  // file: path.
+
+  const namespaceWithURI = await import(
+    "resource://test/data/base_uri_module2.mjs"
+  );
+  const namespaceWithCurrentDir = await import("./base_uri_module2.mjs");
+  const namespaceWithParentDir = await import("../data/base_uri_module2.mjs");
+  const namespaceWithAbsoluteDir = await import("/data/base_uri_module2.mjs");
+
+  return {
+    equal1: namespaceWithURI.obj2 == namespaceWithCurrentDir.obj2,
+    equal2: namespaceWithURI.obj2 == namespaceWithParentDir.obj2,
+    equal3: namespaceWithURI.obj2 == namespaceWithAbsoluteDir.obj2,
+  };
+}
diff --git a/dom/workers/test/xpcshell/data/base_uri_module2.mjs b/dom/workers/test/xpcshell/data/base_uri_module2.mjs
new file mode 100644
index 000000000000..2358d27a8360
--- /dev/null
+++ b/dom/workers/test/xpcshell/data/base_uri_module2.mjs
@@ -0,0 +1 @@
+export const obj2 = {};
diff --git a/dom/workers/test/xpcshell/data/base_uri_worker.js b/dom/workers/test/xpcshell/data/base_uri_worker.js
new file mode 100644
index 000000000000..74137cc20b71
--- /dev/null
+++ b/dom/workers/test/xpcshell/data/base_uri_worker.js
@@ -0,0 +1,27 @@
+// This file is for testing the module loader's path handling.
+// ESLint rules that modifies path shouldn't be applied.
+
+onmessage = async event => {
+  // This file is loaded as resource://test/data/base_uri_worker.js
+  // Relative/absolute paths should be resolved based on the URI, instead of
+  // file: path.
+
+  const namespaceWithURI = await import(
+    "resource://test/data/base_uri_module.mjs"
+  );
+  const namespaceWithCurrentDir = await import("./base_uri_module.mjs");
+  const namespaceWithParentDir = await import("../data/base_uri_module.mjs");
+  const namespaceWithAbsoluteDir = await import("/data/base_uri_module.mjs");
+
+  postMessage({
+    scriptToModule: {
+      equal1: namespaceWithURI.obj == namespaceWithCurrentDir.obj,
+      equal2: namespaceWithURI.obj == namespaceWithParentDir.obj,
+      equal3: namespaceWithURI.obj == namespaceWithAbsoluteDir.obj,
+    },
+    moduleToModuleURI: await namespaceWithURI.doImport(),
+    moduleToModuleCurrent: await namespaceWithCurrentDir.doImport(),
+    moduleToModuleParent: await namespaceWithParentDir.doImport(),
+    moduleToModuleAbsolute: await namespaceWithAbsoluteDir.doImport(),
+  });
+};
diff --git a/dom/workers/test/xpcshell/test_import_base_uri.js b/dom/workers/test/xpcshell/test_import_base_uri.js
new file mode 100644
index 000000000000..7c88a946f4e2
--- /dev/null
+++ b/dom/workers/test/xpcshell/test_import_base_uri.js
@@ -0,0 +1,35 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+add_task(async function testSyncImportBeforeAsyncImportDependencyInWorker() {
+  const worker = new ChromeWorker("resource://test/data/base_uri_worker.js");
+
+  const { promise, resolve } = Promise.withResolvers();
+  worker.onmessage = event => {
+    resolve(event.data);
+  };
+  worker.postMessage("");
+
+  const result = await promise;
+
+  Assert.ok(result.scriptToModule.equal1);
+  Assert.ok(result.scriptToModule.equal2);
+  Assert.ok(result.scriptToModule.equal3);
+
+  Assert.ok(result.moduleToModuleURI.equal1);
+  Assert.ok(result.moduleToModuleURI.equal2);
+  Assert.ok(result.moduleToModuleURI.equal3);
+
+  Assert.ok(result.moduleToModuleCurrent.equal1);
+  Assert.ok(result.moduleToModuleCurrent.equal2);
+  Assert.ok(result.moduleToModuleCurrent.equal3);
+
+  Assert.ok(result.moduleToModuleParent.equal1);
+  Assert.ok(result.moduleToModuleParent.equal2);
+  Assert.ok(result.moduleToModuleParent.equal3);
+
+  Assert.ok(result.moduleToModuleAbsolute.equal1);
+  Assert.ok(result.moduleToModuleAbsolute.equal2);
+  Assert.ok(result.moduleToModuleAbsolute.equal3);
+});
diff --git a/dom/workers/test/xpcshell/xpcshell.toml b/dom/workers/test/xpcshell/xpcshell.toml
index f8b171b89a4e..61b1eef0c25b 100644
--- a/dom/workers/test/xpcshell/xpcshell.toml
+++ b/dom/workers/test/xpcshell/xpcshell.toml
@@ -4,6 +4,9 @@ support-files = [
   "data/worker.js",
   "data/worker_fileReader.js",
   "data/chrome.manifest",
+  "data/base_uri_worker.js",
+  "data/base_uri_module.mjs",
+  "data/base_uri_module2.mjs",
 ]
 
 ["test_ext_redirects_sw_scripts.js"]
@@ -18,6 +21,8 @@ firefox-appdir = "browser"
 
 ["test_fileReader.js"]
 
+["test_import_base_uri.js"]
+
 ["test_remoteworker_launch_new_process.js"]
 # The following firefox-appdir make sure that this xpcshell test will run
 # with e10s enabled (which is needed to make sure that the test case is
diff --git a/js/loader/ScriptLoadRequest.cpp b/js/loader/ScriptLoadRequest.cpp
index 1b3cb52f7206..2c9a7ce8ae4e 100644
--- a/js/loader/ScriptLoadRequest.cpp
+++ b/js/loader/ScriptLoadRequest.cpp
@@ -197,6 +197,22 @@ bool ScriptLoadRequest::IsMarkedForBytecodeEncoding() const {
   return !!mScriptForBytecodeEncoding;
 }
 
+static bool IsInternalURIScheme(nsIURI* uri) {
+  return uri->SchemeIs("moz-extension") || uri->SchemeIs("resource") ||
+         uri->SchemeIs("chrome");
+}
+
+void ScriptLoadRequest::SetBaseURLFromChannelAndOriginalURI(
+    nsIChannel* aChannel, nsIURI* aOriginalURI) {
+  // Fixup moz-extension: and resource: URIs, because the channel URI will
+  // point to file:, which won't be allowed to load.
+  if (aOriginalURI && IsInternalURIScheme(aOriginalURI)) {
+    mBaseURL = aOriginalURI;
+  } else {
+    aChannel->GetURI(getter_AddRefs(mBaseURL));
+  }
+}
+
 //////////////////////////////////////////////////////////////
 // ScriptLoadRequestList
 //////////////////////////////////////////////////////////////
diff --git a/js/loader/ScriptLoadRequest.h b/js/loader/ScriptLoadRequest.h
index ce19c94978d7..ea1467134c5c 100644
--- a/js/loader/ScriptLoadRequest.h
+++ b/js/loader/ScriptLoadRequest.h
@@ -203,6 +203,13 @@ class ScriptLoadRequest : public nsISupports,
   const LoadedScript* getLoadedScript() const { return mLoadedScript.get(); }
   LoadedScript* getLoadedScript() { return mLoadedScript.get(); }
 
+  /*
+   * Set the request's mBaseURL, based on aChannel.
+   * aOriginalURI is the result of aChannel->GetOriginalURI.
+   */
+  void SetBaseURLFromChannelAndOriginalURI(nsIChannel* aChannel,
+                                           nsIURI* aOriginalURI);
+
   const ScriptKind mKind;  // Whether this is a classic script or a module
                            // script.